#include <vector>
#include <iostream>

using namespace std;

class Solution
{
public:
    void reverseString(vector<char> &s)
    {
        auto begin = s.begin();
        auto end = s.end() - 1;
        while (begin != end)
        {
            swap(*begin, *end);
            begin++;
            if (begin == end)
            {
                break;
            }
            end--;
        }
    }
};
